We consider the number N (θ) of eigenvalues e iθ j of a random unitary matrix, drawn from CUE β (N ), in the interval θj ∈ [θA, θ]. The deviations from its mean, N (θ) − E(N (θ)), form a random process as function of θ. We study the maximum of this process, by exploiting the mapping onto the statistical mechanics of log-correlated random landscapes. By using an extended Fisher-Hartwig conjecture supplemented with the freezing duality conjecture for log-correlated fields, we obtain the cumulants of the distribution of that maximum for any β > 0. It exhibits combined features of standard counting statistics of fermions (free for β = 2 and with Sutherland-type interaction for β = 2) in an interval and extremal statistics of the fractional Brownian motion with Hurst index H = 0. The β = 2 results are expected to apply to the statistics of zeroes of the Riemann Zeta function.